Glass tube baking apparatus



June 29, 1943; R. M. GARDNER GLASS TUBE BAKING APPARATUS Filed May 28, 1941 {Sheets-Sheet 1 zeoz naMaaumgm June 29, 1943. R M, GARDNER 2,323,214

GLASS TUBE BAKING APPARATU Filed May 28, 1941 4 Sh'eets Sheet 2 June 29, 1943, R. 'M. GARDNER 2,323,214

GLASS TUBE BAKING APPARATUS Filed May 2 8, 1941 4 Sheets-Sheet s Q Gqfdneymvmfog ATTORNEY I June 29, 1943. M, GARDNER 2,323,214

GLASS TUBE BAKING APPARATUS Filed May 2 8, 1941 4 She ets- -Sheat 4 k B *W WT WWWTWIW l Q I D A i I A L L; T L

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, ATTORNEY Patented June 29, 1943 GLASS TUBE BAKING APPARATUS Roland M. Gardner, Swampscott, Mass assignor to Syivania Electric Products Inc., a corporation of Massachusetts Application May as, 1941, Serial No. 395,555

Claims.

This invention relates to heating ovens and more particularly to an oven for baking the coating of luminescent material applied to the walls of an elongated glass tube.

An object of this invention is to provide a heating oven in which elongated tubular glass envelopes may be baked.

Another object is to provide such an oven with means by which the tubular glass envelopes may be caused to pass therethrough.

A further object is to provide a smooth .rotating surface for conveying the tubing through the oven.

Another object is to provide a tubing conveyor means which will keep the tubing straight and properly annealed.

A further object is to provide a means for feeding said tubular glass envelopes into said oven and means for ejecting the same there= from.

Further objects, advantages, and features will be apparent from the following specification taken in conjimction with the accompanying drawings in which:

Figure l is a projection of the'tube baker shown partly in section.

Figure 2 is a composite side elevation of the oven taken along the lines AA, BB, C-C respectively-of Figure 6.

Figure 3 is a side elevation in section taken along the line D-D of Figure 6 showing the heat expansion equalizer assembly.

Figure 4 is a projection of the tubing etching device and the conveyor on which the etched tubing is carried into the oven.

Figure 5 is an end view partly in section of the tubing conveyor assembly, taken along the line E-E in Figure 4.

Figure 6 is a plan view of the belt of rollers.

Figure 7 is an end view in section showing the roof and side wall construction and the assembly for conveying the tubing through the oven.

Figure 8 is a sectional view of the air manifold assembly.

Figure 9 is a section showing the structure of the roof of the oven.

This heating oven is an improvement over that described in the copending application Serial No. 316022, filed January 27, 1940, and issued as Pat out No. 2,267,727, dated December 30, 1941. In an even of the type herein described, the bulbs or tubes are carried through an oven on a belt of rollers l. Each roller ihas along rod 2 extending therethrough. The side walls of the oven consist of two long channel iron sections,

the upper wall 3 and the lower wall 22. These walls are sumciently' spaced to permit the ex tension therebetween of the rods-2. These rods are supported at each end by a series of small rollers 4 on the outer ends thereof. These rollers run along the track 2! which is supported from the lower side wall 22 of the oveni To insure rotation of the rollers I one end of the rods 2 which pass therethrough has the gears 40 attached thereto as well as rollers i. These gears 40 run on a rack 36 which, like the roller track 2! is also supported from the 'lower side wall 22 of the'oven. As was pointed out above, the main support of the rods 2 is through th rollers i. There is just enough weight on the rack 36 through the gears 68 to provide for the rotation of'the rollers l, and still not enough weight to cause any binding.

The rods 2 are. led through the oven by a pair of endless chains 5, with attachments 66 as later described for leading and maintaining spacing of the rollers, one on each end of the rods. These chains are turned through a driven sprocket 6 on the driven shaft '5 by the drive chain 8 from the drive sprocket 9 and drive shaft Ill project- I ing from the speed reducer H which reduces the speed of the motor l2 through the belt 13 and the wheels 94 and l5.

- The burners l6, projecting through the roof of the oven from the burner headers ii, are mounted through the channel iron units l8 which form the roof of the oven. Magnesia heat insulating blocks i9 are inserted in the channels of the channel iron units it and are held therein by a covering-of stainless steel sheets 29. Thus it is apparent that with this type of roof construction, one or more rows of burners may readily be removed for cleaning or replacement service. The side walls 3 and 22 of the oven are constructed in the same manner as the roof, i. e., the channel iron units have a filling of insulating material therein and a covering of stainless steel. Stainless steel is used as a covering on the walls and the roof and also as the material from which the rollers i are formed because of its high degree of heat reflectivity and immunity to scaling at relatively high temperatures.

The oven is supported from the channel iron side walls 3 and 22 by the supporting frame 24 through the I-beams 37 as shown in Figure 2.

The tubing is ejected onto the table 28 from the rollers by the ejector bars 25 asmore clearly shown in Figure 2. The canopy 26 and the duct 2'! serve as a means through which the gases formed by the carbonization of the nitrocellulose binder in the fluorescent coating may be drawn oif through end spaces parallel to channel units I! in an arrangement similar to that in Figure 4 of Patent No. 2,267,727, issued December 30, 1941. This was a copending application Serial No. 316,022, filed January 27, 1940. Much of the excess heat given off by the oven may be drawn oif by connecting the duct 21 to an evacuating means. The evacuation of these gases being given off by the baking of the tubing may be further aided by the use of an air duct or manifold of the type described below in conjunction with Figure 8. However similar means, such as those described in co-pending application Serial No. 346,617, filed July 20, 1940, and issued as Patent No. 2,289,354, dated July 14, 1942, or in Patent No. 2,27,727, referred to above, may also be used without departing from the spirit of this invention.

Figure 2 is a side view in section of a part of the machine, particular attention being paid to the internal structure of the rollers I and the manner in which the rods 2 therethrough are held. The rods 2 are held within the rollers l in a manner to minimize the possibilities of wide of contact on the inner wall of the roller l are slightly rounded to provide sufilcient contact surface to insure a pos.tive support. The disk 10, see lower left of Figure 2, fitted in the ends of each roller l, and on the ends of the rods 2 and are not closely fitted withrespect to the roller l but rather are loosely fitted so as to provide for any thermal expansion thereof.

By using a collar 29 with its corners slightly rounded rather than a disk which would give a 360 degree contact area, the danger of the rods 2 becoming distorted and out of shape as a result of excessive heat conducted thereto through the supportingmeans is minimized. So also is the danger of cold spots on the rollers minimized for the contacts on the rollers by the rod supporting'means is kept at a minimum and thus a minimum amount of heat is conducted 08 from the surface of the rollers. As is shown in Figure dinally on any two adjacent rollers. This staggering is such that the section of Figure 2. upper left, shows a collar 29 in alternate rollers only. This is further protection against strains being set up in the tubing being baked, for any slight temperature variations in the roller i will not be concentrated at one point on the-tubing as it would be if the collars 29 were located inthe same position longitudinally on all the: rollers.

'As was pointed. out above in connection with Figure 1,this baking oven is capable of baking tubing of small diameters. When the tubing has been baked it is ejected from the oven by an elector bar 25 as shown in Figure 2. There are a series of such ejector bars projecting from a wheel 3| keyed to the driven shaft 1. These b rs 2! are held in position relative to the wheel II by a spring 32 in an elongated slot 24 in the wheel 2|, and the pin 32 lying in a slot 24 in the bar 25. The spring 92 is normally expanded, projecting the bar 25 outwardly. As the wheel 3! turns, the several ejector bars 2! successively come in contact with one of the rollers l and are consequently pushed down into their respective elongated slots 24, causing the associated spring 22 to contract.

As is shown in Figure 2, the rollers I spread apart somewhat as they finish their jobof carrying the tubing, move downward, and start the return to the front of the oven to renew the tubecarrying cycle. Since the distance between the ejector bars is always constant, the increased spacing between the rollers i permits the ejector bars to move into this space. When the ejector bar is freed from its contact with the roller, the spring 32,'previously contracted, will expand and the bar will eject the tubing 95. a

Figure 3 shows the heat-expansion equalizer employed to provide for the expansion of the lower side wall 22 of the even so that expansion of the channel iron 22 will not cause the chain 5 to become excessively taut. The angle iron 38 is bolted to the channel iron 22. The gear 40' on which the chain 5 travels turns about the shaft 4 I. The bars 39 are supported by the bar support 42 and extend through the bar guide 49 about the shaft ll and through openings provided therefor in the angle iron 29. Thus when the channel iron 22 expands, the expansion will be taken up by the springs 44 on the bars 39, the angle iron 38 merely sliding along the bars 39 and exerting a contracting pressure on the springs by pressing the springs up against the bar guide 42. Thus the desired tension may be kept on the chain 5 at all times and the expansion of the channel iron 22 will be absorbed by the contraction of the springs 44.

Figure 4 shows the combination etching device and mechanism for feeding the tubing into the baking oven. The top portion of this may be seen in Figure 1 but it appears more clearly in Figure 4. The table 45 is supported on the legs 46. The frosted glass window 47 set in the top of the table is located over a light source encased in the housing 42. Thus tubing or bulbs, about to be etched and baked may first be inspected for coating defects.

The tubing is properly centered with respect to the etching stamps 50 by the guide ii. The tubing is rolled down the inclined blocks 52 sothat the tubing comes in contact with the etching stamps 99, and rolls down further to be picked up by the conveyor wheels 52. There are a series of conveyor wheels 52 paired of! with a series of friction wheels 54. The friction wheels turn faster than the conveyor wheels so that the tubing is rotated as it is being carriedby the conveyor wheels thus enabling the burners $5 to properly burn in the etching on the tubing before the tubing rolls out of the conveyor wheel and along the arms H into the oven. 1 r

The driven shaft 56 on which the conveyor and friction wheels turn is driven through the driven to the burners 55 through the connecting lines 92, and the arms ll along which the tubing rolls from the conveyor wheels into the oven.

Figure 6 is a plan view of the oven without the roof. It shows more clearly the relative location of the rollers 4 and the gears 40. It also shows the location at which the various sections shown in Figures 2 and 3 were taken. The section AA is the one taken to depict the manner in which the ejector bars 25 operate as shown in the upper left portion of Figure 2. The section BB is the one taken to depict the structure shown in the lower left portion of Figure 2. The section C-C is the one taken to depict the manner in which the endless chain and the gears 40 and rack 36 operate as shown in the right hand portion of Figure 2. The section D-D is the one taken to depict the manner in which the heat expansion equalizer operates as shown in Figure 3.

Figure 7 shows how the rollers I, the rods 2, and their associated assembly is constructed to provide for expansion due to heat generated dur ing the operation of the oven. The roller 4 on the rod 2 runs along the track 2! provided therefor. This track is supported from the lower side wall 22 of the oven by the supporting arm 63. The endless chain 5 which carries the rollers I through the oven has an attachment 64 projecting up from the links of the chain. This attachment has a hole in the face thereof sufficiently large for the rod 2 to pass therethrough. There is one of these attachments for each rod and roller. In this manner the chain 5 carries the rollers I through the oven. The gears 40 on the rack 36 provide the means through which'the rollers are rotated as they pass through the oven. This rack is supported from the lower side wall 22 of the oven by the supporting arm 64'.

It should be noted in this figure, Figure 7, how the rollers 4, the gears 40 and their respective tracks are located in relationship to each other with respect to providing for thermal expansion. It is the outer end of the roller 4 which normally rides on the track 2|. When expansion of the rod 2 takes place, the roller 4 may move out slightly with respect to the track 2|. When this takes place, the roller will still ride on the track 2| for then its middle or its inner end will be in contact with the track. The same provision has been made with respect to the gear 40 and the rack 36. The gear 60 normally rides on the inner side of the rack 36. When expansion takes place it may move to the middle or the outer side of the bar and still function efliciently and properly.

Figure 7 also shows how further insulation may be obtained by providing two or more layers of channel irons filled with insulating material to form the roof of the oven through which the burners extend.

Figure 8 shows how an air manifold may be employed to aid in the evacuation of the gases given off during the baking process. The air manifold 65 is supported from the upper side wall 3 of the oven by the arm 66. The several connecting air lines 61 extend downward from the manifold 65 and terminate at a point slightly above the rollers I. of these several air lines 61 there is a small vent 68. This vent is located in a position where the air blowing therefrom will blow into one of the ends of the tubing 89. Thus this air manifold At a point near the bottom apparatus serves a very definite aid to proper and I complete evacuation of the gases through the duct 21 as shown in Figur 1.

It should be noted that the air manifold shown in Figures 7 and 8 is adjustable as to height and as a result the efficiency of the manifold assembly is increased. Maximum efliciency is obtained when the stream of air emanating from the ports 68 is directed into the center of the tubing being baked. The manifold 65 is supported by the curved inner endof arm 66. This arm extends through 'a horizontally extending, vertically elongated opening H in side wall 3 and is locked in adjusted position by nut 13, threaded on arm 66 and bearing on plate 12 which straddles opening H to bear on side wall 3. Tightening of nut 13 draws the curved inner end of arm 66 against the manifold 65 to press it against the side wall 3. When it is desired to vertically adjust the manifold, nut 13 is loosened, and arm 66 moved vertically in opening H.

Figure 9 shows in detail just how the channel iron units are assembled to form the roof of the. oven. The channel of the channel iron i8 is filled with the insulating material! and the stainless steel sheets 20 which are wrapped around the channel iron serve to keep this insulating material in place and to reflect the heat from the burners down onto the tubing being baked. By using separate sheets of stainless steel for each channel iron, each channel iron assembly forms a. separate, independent unit.

What I claim is:

'1. An oven for baking glass tubing having: a

series of spaced rollers; means for rotating said rollers; means for moving said rotating rollers through said oven; 2. series of ejector bars at the exit of said oven; and spring actuated means for causing said ejector bars to project themselves into the space between said rollers.

2. An oven for baking glass tubing, said oven comprising: a series of spaced rollers; means for rotating said rollers; means for moving said rotating rollers through said oven; apparatus for feeding said tubing onto said rollers; and spring-actuated means for electing the tubing from said rollers at the exit of said oven.

3. The oven of claim 2 and a manifold inside the oven for directing air into one end of the tube being baked.

4. An oven for baking tubes of glass or the like comprising: a series of spaced refractory rollers on which said tubes may be placed; mechanism for rotating said rollers; a frame of channel irons above and spaced from said rollers, said channel irons being placed with the open ends of the. channels facing the rollers; a series of stainless steel channels covering the open ends of the iron channels; and a series or burners between the steel channels and the rollers to direct heat downwardly towards the rollers. I

5. The oven of claim 2 and a manifold inside the oven for directing air into one end of the tubing being baked, the manifold being adjustableto direct the stream of air into the center of the end of said tubing.

ROLAND M. GARDNER. 

